The invention relates to a carrier for disk-shaped articles, especially for silicon wafers during etching thereof, with an annular nozzle in the preferably round carrier surface facing the article, to which pressurized gas is supplied, and with at least one annular projection which is provided on the carrier surface facing the article and which is used as a support for the article and which is located within the annular nozzle.
A carrier of this type for disk-shaped articles of the initially mentioned type which holds in place the articles exclusively based on the negative pressure which arises due to the Bernoulli principle is known from EP 611 273 A.
One difficulty in these known carriers according to the Bernoulli principle consists in that the disk-shaped articles essentially float on the gas cushion and therefore are not always securely held in place to an adequate degree.
The object of the invention is to improve the known carrier proceeding from EP 611 273 A such that reliable holding of disk-shaped articles is possible while they are being treated with treatment liquid without the need of retaining cams which are to be placed against the edge of the disk-shaped article and such that the article, even without negative pressure being formed due to the Bernoulli principle, is held securely enough for the stipulated actions.
According to the invention, this object is achieved by the fact that in the surface facing the article within the annular projection, there is at least one opening supplied with negative pressure.
In the carrier according to the invention, the disk-shaped article is drawn against the annular projection provided in the carrier surface facing the article. Since the projection in the invention engages the disk-shaped article off its center, the article is securely held during treatment (no danger of tilting) and the article can be rotated by turning the carrier since the projection engages the article off center and therefore torques can be transmitted from the carrier to the disk-shaped article. Because within the annular projection there is an opening supplied with negative pressure in the carrier surface facing the disk-shaped article, a sufficient contact pressure is reached between the projection and the article. In addition, an advantage arises which consists in that the treatment medium in the case of a fracture of the disk-shaped article is exhausted by the carrier and cannot reach downstream system parts.
One embodiment of the invention provides that the annular projection is an annular rib on the carrier surface facing the disk-shaped article. In this embodiment, the annular rib which forms at least one annular projection is formed preferably in one piece with the carrier part which lies inside the annular nozzle and projects above the carrier surface which faces the disk-shaped article.
The invention also extends to an embodiment in which it is provided that there are several annular projections concentric to one another. To guarantee that also between the annular projections negative pressure prevails which moves the disk-shaped article against the annular projections, it can be provided that within the innermost annular projection and between the annular projections there is at least one opening each supplied with negative pressure. In an alternative embodiment it can be provided that within the outermost annular projection there is at least one opening supplied with negative pressure and that each annular projection with the exception of the outermost projection is interrupted at least once. In this embodiment, the opening supplied with negative pressure can be located anywhere within the outermost annular projection, therefore also within the innermost annular projection or between annular projections that are adjacent to one another.
The annular projection need not be formed in one piece with the carrier, but it can also be a ring inserted into the carrier surface facing the article.
It can be advantageous if the annular projection is resilient in the direction perpendicular to the carrier surface facing the article. In this way, the projection yields elastically in the direction to the carrier surface facing the disk-shaped article so that an equilibrium state arises which precludes deformations of the disk-shaped article, as can occur in a rigid projection which fits tightly only in the center of the article according to EP 48 995 A if the projection is not correctly dimensioned. Still, the disk-shaped article is also held securely in place in the direction parallel to the carrier surface facing the article such that it can be treated with a treatment liquid and can be turned to spin the latter off.
In a three-dimensionally especially favorable embodiment of the invention, it can be provided that the annular projection is located concentrically to the axis of the carrier.
One embodiment of the invention calls for the fact that the annular projection is supported against the carrier by elastic elements. In this way, resiliency can be achieved independently of the material which comprises the annular projection. In this case it can be provided in a simple embodiment that the elastic elements are helical springs.
In the invention, it can be provided that the annular projection is inserted into an annular groove or into a circular depression in the carrier surface facing the article. In this embodiment, the fit of the annular projection on the carrier is achieved in a special manner.
In one embodiment of the carrier according to the invention, the annular projection consists of teflon-coated silicone. In this embodiment as well the material of the ring is not attacked by the treatment medium even if it is an acid.
One embodiment can still be characterized in that the annular projection is hollow. For this reason the annular projection is easily elastic enough.
Another embodiment of the carrier according to the invention is characterized in that a line proceeds from the opening and leads to a means which produces negative pressure. In this embodiment, it is especially easy to supply negative pressure to the opening provided within the annular projection.
If according to one proposal of the invention it is provided that the means which produces negative pressure is an injector nozzle, the advantage arises that the means which produces the negative pressure can be operated by the compressed gas supplied to the annular nozzle of the carrier and separate pumps or the like are unnecessary for supplying the opening within the annular projection with negative pressure.
In another embodiment of the invention, it can be provided that pressurized gas which is supplied to the annular nozzle flows through the injector nozzle. In this embodiment, mechanical moving parts are unnecessary so that a durable and still reliable construction results.
One arrangement which is especially three-dimensionally favorable arises when the means which produces negative pressure is located in the carrier.